Oldest-Known Asteroids in Solar System Identified

by SPACE.com Staff | March 24, 2008 09:30am ET

Three rocks hurtling through space appear to be among our
solar system's oldest objects.

The ancient asteroids
seem to have formed some 4.55 billion years ago, making them older than the
oldest meteorites ever found on Earth, said Jessica Sunshine, an astronomer at
the University of Maryland who led the team that discovered the objects.

"We have identified asteroids that are not represented
in our meteorite collection and which date from the earliest
periods of the solar system," Sunshine said. "These asteroids are
prime candidates for future space missions that could collect and return
samples to Earth providing a more detailed understanding of the Solar System's
first few millions of years."

The scientists observed the asteroids with infrared and
visible light telescopes on Hawaii's Mauna Kea. They measured the various
amounts of different colors of light reflected from the surface and found
evidence that the asteroids contain bits of material rich with calcium and
aluminum.

An abundance of these elements indicates that the objects were
formed when the solar system was young because during that time the first
materials to condense into solid particles were rich in calcium and aluminum.

These three asteroids
contain two to three times the amount of calcium- and aluminum-rich material of
any space rock found on Earth.

The discovery was detailed in the March 20 online edition of the
journal Science.